Help: How to Fix 130XE RAM?

[arkanoid]

Hi Atarians!

 

I am looking for some tips/info/help for me to repair my poor 130XE :-(

 

I have just bought myself an 130XE. Today it worked fine for a short period (about 1 hour). But now when I turn it on it only displays the "Memory Test" screen whith some RAM errors. I don't know what heppened, but I can only think some electric spike happened. Maybe from RF connection from this DUMB LCD TV (CRT is best!) as it was giving me small shocks when I plugged in the Atari's RF cable. Is this possible?

 

I don't know if this will help but here is the RAM Error pattern:-

 

G = Green Square

R = Red Square

 

GGGGGGGGGGGGGGGG

GRGRGGGRGRGRGRGR

GGGGGGGG

 

40 Squares Total

 

Can I use this to tell exactly which RAM chips are broken somehow? Does this pattern mean something useful?

 

I'm not a expert but it looks like damaged RAM here or am I mistaken? both ROM blocks passes the test OK (Green) so I'm thinking it's not ROM...? I have 16 old working ATARI STe RAM ICs from upgrade modules. They are model: Siemens HYB 41256-10 (9038). They are same phiysical size and DIP as in XE. Are these compatible with the 130XE? If they are no good where can I find some compatible for XE?

 

I really want to fix this great computer. :-( I hope someone can guide me to get it right. Is there some guides to fixing the XE RAM and some schematics?

 

Thank you for your help!

 

PS: also, is this the best place to ask for this help or is there another forum? (sorry I'm new to Atari scene)

Edited April 2, 2007 by arkanoid

[tjlazer]

Have you searched on here and other sites? (Google)? Most of your questions are easily found.

[+Guitarman]

Keep the 41256's as they will be useful in modding the 130XE to 320K!!! But... for testing, you will need some known good 4164's. This should be what's installed in the 2 banks of ram on the board. Chances are the ram in your 130XE is NOT socketed, which makes it even harder. There was another user on the forum (Tezz) who had this same issue. 130XE's are known for having flaky ram.

 

The easy way out is to cut out the current ram, remove the left over pins, install sockets and replace it all with known good ram chips. If you are careful with cutting out the current chips, with a little care and tweaking of the legs, the good ones can be used again. Once you install all good ram, then you can remove one chip and replace it, one by one, with the old chips and find which ones cause red squares. Toss the bad ones and keep the good ones as extras. This is the most direct and efficient way to get it fixed.

[Tezz]

Hi Atarians!

 

I am looking for some tips/info/help for me to repair my poor 130XE :-(

 

I have just bought myself an 130XE. Today it worked fine for a short period (about 1 hour). But now when I turn it on it only displays the "Memory Test" screen whith some RAM errors. I don't know what heppened, but I can only think some electric spike happened. Maybe from RF connection from this DUMB LCD TV (CRT is best!) as it was giving me small shocks when I plugged in the Atari's RF cable. Is this possible?

 

I don't know if this will help but here is the RAM Error pattern:-

 

G = Green Square

R = Red Square

 

GGGGGGGGGGGGGGGG

GRGRGGGRGRGRGRGR

GGGGGGGG

 

40 Squares Total

 

Can I use this to tell exactly which RAM chips are broken somehow? Does this pattern mean something useful?

 

I'm not a expert but it looks like damaged RAM here or am I mistaken? both ROM blocks passes the test OK (Green) so I'm thinking it's not ROM...? I have 16 old working ATARI STe RAM ICs from upgrade modules. They are model: Siemens HYB 41256-10 (9038). They are same phiysical size and DIP as in XE. Are these compatible with the 130XE? If they are no good where can I find some compatible for XE?

 

I really want to fix this great computer. :-( I hope someone can guide me to get it right. Is there some guides to fixing the XE RAM and some schematics?

 

Thank you for your help!

 

PS: also, is this the best place to ask for this help or is there another forum? (sorry I'm new to Atari scene)

You will just have a few bad ram chips that you will need to desolder and replace. If you have spare ram chips from another Atari, you can piggyback the ram on top the existing ram one at a time to see which one is bad. The ram used in the XE range were of a poorer quality than the xl's and prone to failure so if you have the patience it would be advised to replace them all with 41256 ram chips. Anything between 100ns and 150ns will be ok to use. Desolder the ram chips, install low profile 16-pin sockets and insert you new ram chips. It is easy also to mod this set-up to achive higher ram, like 320k for instance using the Scott Peterson method

 

Here's a link to the schematics..

http://www.dereatari.republika.pl/schematy.htm

 

Regards,

Tezz

Edited April 2, 2007 by Tezz

[Tezz]

LOL, in the time it took me to reply Guitarman already answered ..

[+Guitarman]

Edited April 2, 2007 by Guitarman

[re-atari]

Hi Atarians!

 

I am looking for some tips/info/help for me to repair my poor 130XE :-(

 

I have just bought myself an 130XE. Today it worked fine for a short period (about 1 hour). But now when I turn it on it only displays the "Memory Test" screen whith some RAM errors. I don't know what heppened, but I can only think some electric spike happened. Maybe from RF connection from this DUMB LCD TV (CRT is best!) as it was giving me small shocks when I plugged in the Atari's RF cable. Is this possible?

 

Can I use this to tell exactly which RAM chips are broken somehow? Does this pattern mean something useful?

 

I'm not a expert but it looks like damaged RAM here or am I mistaken? both ROM blocks passes the test OK (Green) so I'm thinking it's not ROM...? I have 16 old working ATARI STe RAM ICs from upgrade modules. They are model: Siemens HYB 41256-10 (9038). They are same phiysical size and DIP as in XE. Are these compatible with the 130XE? If they are no good where can I find some compatible for XE?

 

I really want to fix this great computer. :-( I hope someone can guide me to get it right. Is there some guides to fixing the XE RAM and some schematics?

 

A spike could very well have been the cause of your troubles, although I always was under the impression that IC's are relatively safe once they are in place (i.e. when they have their GND pin connected). I personally have never had an IC fail through ESD, but I guess strange things can happen in extreme cases...

 

In selftest each block represents a 1K memoryblock. If you switch on your XE with the OPTION key pressed, it should show 48 blocks. The remaining space (16K) is occupied by the OS rom.

 

XE's DRAM is known to fail at this age, so it's probably not a bad idea to start by swapping them. You can use the DRAM's you mention as substitutes, they are pincompatible with the 4164's but have an extra addressline (A8). If you decide to replace the DRAM's do not solder the replacements in directly, use good quality sockets instead. It will make troubleshooting which specific DRAM is defective, if you wanted to find out later on, so much easier.

 

You should be able to find a couple of quite recent threads about desoldering and replacing DRAM's in 130XE's, 65XE's and 800XL's in this forum. Check Tezz's threads, he has been doing this with good result the last few weeks, and has kept a detailed log of how he went about.

 

BTW: in an unmodded XE your 41256's will only show 64K per memorybank, but provide room for 256K. Once you have the system back on its feet again, you could add some circuitry to make this extra memoryspace available. The 130XE can be modded to 320K by replacing one of the memorybanks.

 

re-atari

[arkanoid]

thank you guys _very_ much for your replies. lots of very helpful info! I don't know how I missed Tezzer's great log, earlier but I have just now read it and found it very helpful! it's made my mind clear to what I have to do now.

 

I seem to have the crappy MT4264 RAM chips in my XE which is probably why they are now broke. so after reading this forum I have decided to remove and replace ALL 16 of these chips with my 16 Siemens HYB41256-10's. I don't want to keep ANY of those crappy MT4264's... because even if some work ok now they will probably break very soon. I will add DIL socket's first to make testing and replacing chips easier in future. i have just ordered the sockets from eBay, so I will let you guys know how it goes!

 

one thing i'm not sure about. atm i just want to get my XE up and working and adressing 128k (130xe) of memory and I think putting my 16 HYB41256 IC's in BOTH banks will do this ok. (??) *BUT* after I have it working I might want to do the 320XE upgrade. I have read Scott Peterson's 130 > 320 upgrade and it seems to be based on one bank of 64k chips and one bank of 256k chips. does anyone know if the hack will work with TWO banks of 256 chips? or do they have to be one 64 one 256 bank?

Edited April 2, 2007 by arkanoid

[Rybags]

Those memory chips are 1 bit, which means that 8 of them are involved in every memory access.

 

Maybe the fault is elsewhere, such as in the addressing or decoders?

 

All your fails appear to be happening in the 16-32K range, which just also happens to be where extended banking takes place.

Edited April 3, 2007 by Rybags

[Tezz]

does anyone know if the hack will work with TWO banks of 256 chips? or do they have to be one 64 one 256 bank?

It'll work fine with both banks replaced with 41256 256 ram, the left bank still utilises 64k, the extended right bank of normally a further 64k is used in the modification to access the otherwise inaccessable extra mem of the 41256 chips.

 

It's well worth socketing the board either way to diagnose and easily deal with problems in the future (although you will prob be ok for a long time with those ram chips changed ) it'll also make it easier to diagnose incase it is something other than the ram as Rybags suggests. I'd order a few more 41256 ram chips than you need so you can swap a few to discount any of the new ones being bad if the problem still persists when you've replaced them.

 

Good luck